Many electrical components have a tendency to fail at some point in time. Components may fail for a wide variety of reasons including, for example, overheating, manufacturing defects, component material fatigue or breakdown, and excessive current, to name but a few.
In many electronic and electrical devices it is helpful to be able to quickly identify failed components so that they may be replaced.
Some electrical components provide electrical diagnostic signals that enable a monitoring circuit or module to determine the state of a component. For example, some electrical motors or fans provide diagnostic signals in the form of an electrical waveform having a frequency proportional to the speed of the motor. A monitoring circuit may then determine the speed of the motor, using the diagnostic signal, and may hence determine whether the motor is operating correctly or not.
Such diagnostic signals may be useful when a single component is to be monitored, but may be unmanageable when a large number of components require monitoring. For example, some electronic devices, such as industrial printers, may include 30 or more fans, that are used for device cooling or for drying ink.
When arrays of electrical components are to be monitored, the diagnostic signals from each component generally have to be individually connected to individual monitoring circuits. This is because electrically connecting diagnostic waveform signals together results in a waveform from which it is difficult to determine which diagnostic signal relates to which component. Furthermore, the additional wiring necessary for connecting individual diagnostic signals to individual monitoring circuits increases the associated complexity and cost.